EP0205708A2 - Verfahren zur Herstellung von Kaliumphosphat durch Ionenaustauschen - Google Patents

Verfahren zur Herstellung von Kaliumphosphat durch Ionenaustauschen Download PDF

Info

Publication number
EP0205708A2
EP0205708A2 EP85308710A EP85308710A EP0205708A2 EP 0205708 A2 EP0205708 A2 EP 0205708A2 EP 85308710 A EP85308710 A EP 85308710A EP 85308710 A EP85308710 A EP 85308710A EP 0205708 A2 EP0205708 A2 EP 0205708A2
Authority
EP
European Patent Office
Prior art keywords
potassium
phosphate
ion exchange
salt
resin
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP85308710A
Other languages
English (en)
French (fr)
Other versions
EP0205708A3 (de
Inventor
W. Wes Berry
William R. Erickson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Advanced Separation Technologies Inc
Original Assignee
Progress Equities Inc
Advanced Separation Technologies Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Progress Equities Inc, Advanced Separation Technologies Inc filed Critical Progress Equities Inc
Publication of EP0205708A2 publication Critical patent/EP0205708A2/de
Publication of EP0205708A3 publication Critical patent/EP0205708A3/de
Ceased legal-status Critical Current

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/30—Alkali metal phosphates

Definitions

  • the present invention relates to a process for producing potassium phosphate and more particularly to an ion exchange process wherein a metal phosphate salt solution is passed through a potassium loaded exchange resin so as to effect an exchange of potassium and the metal.
  • potassium phosphate is a very effective fertilizer. Additionally, since it may be used with very little inert material present, it is easier to apply and may be transported relatively inexpensively.
  • an ion exchange process for producing potassium phosphate which utilizes the potassium sulfate by-product from processes for the recovery of aluminum from alunite. More specifically, potassium ions from potassium sulfates are loaded onto a resin and then exchanged with phosphoric acid to yield the potassium phosphate.
  • an object of the invention to provide a-process for producing potassium phosphate continuously and with a higher degree of efficiency than heretofore possible by employing in conjunction with said process an Advanced S epara- tion Device (ASD) which enables the effluent streams of each of the processing stages, having depleted levels of reactant, to be simultaneously and continuously fortified in an intra-stage fashion with additional reactant material.
  • ASD Advanced S epara- tion Device
  • an ion exchange process for producing potassium phosphate from a metal phosphate salt and potassium loaded resin using the ASD which comprises a plurality of resin-filled chambers which rotate about a circular path in periodic fluid communication with a plurality a fixed feed and discharge ports located at opposite ends of the chambers.
  • the process may be carried out in four stages, each stage corresponding to one or more fixed feed ports.
  • the first stage is an ion exchange process wherein a phosphate salt solution passes through one or more fixed feed ports and is delivered to the potassium-loaded resin to produce potassium phosphate and a resin loaded with the cation of the salt.
  • a washing fluid is passed through a first set of one or more fixed washing fluid feed ports where it is then delivered to the cation-loaded resin so as to remove any entrained potassium phosphate solution or unexchanged metal phosphate salt material.
  • a regeneration fluid such as potassium chloride is then supplied to the cation-loaded resin so as to form regenerated potassium loaded resin and the chloride salt of the cation.
  • a second washing fluid feed is supplied to a second set of one or more fixed washing fluid feed ports where it is then delivered to the potassium loaded resin so as to remove residual amounts of the chloride salt of the cation or potassium chloride.
  • the above-described ASD arrangement makes it possible to add additional calcium phosphate or pH adjusting materials during the course of the ion exchange process thus allowing for a more complete reaction and more efficient utilization of the resin.
  • the process of the present invention is carried out in the Advanced Separation Device (ASD) which enables continuous ion exchange between the calcium phosphate feed solution and the potassium loaded resin when incorporated with the overall process of the present invention.
  • ASD Advanced Separation Device
  • the ASD is described in detail in assignee's copending application Serial No. 713,492, filed March 19, 1985, the disclosure of which is hereby incorporated by reference.
  • Fig. 1 Before describing the application of the ASD device to this process, reference is made to the block diagram of Fig. 1 where the overall ion exchange process is set forth. Although the process is described in terms of a calcium phosphate feed, it will be appreciated that any phosphate salt feed material may be used for exchange with the potassium loaded resin so long as the exchange salt of the cation of the the phosphate salt feed is water-soluble.
  • a monocalcium phosphate solution (monocal) is first prepared by combining phosphoric acid and phosphate rock.
  • the solids Once the solids have been removed from the monocal solution, it is sent to the ASD for contact with a potassium loaded ion exchange resin where an exchange of potassium for calcium and hydrogen occurs so as to produce a resin loaded with calcium and a water soluble potassium phosphate product, which may then be sent off to a fertilizer preparation facility.
  • a potassium loaded ion exchange resin where an exchange of potassium for calcium and hydrogen occurs so as to produce a resin loaded with calcium and a water soluble potassium phosphate product, which may then be sent off to a fertilizer preparation facility. Due to the unique nature of the ASD, it is possible during this ion exchange stage to fortify the partially exchanged monocal solution, i.e., the solution containing potassium phosphates as well as unexchanged monocal, with additional fresh calcium phosphate material so as to increase the concentration gradient of calcium to potassium thereby increasing the efficiency of exchange.
  • a potassium regeneration solution such as potassium chloride is fed into the ASD so as to effect reloading of the resin with potassium while stripping away the calcium in the form of water soluble chloride.
  • the starting material may be calcium phosphate solution and more particularly; a monocalcium phosphate (monocal) solution produced by combining phosphate rock and phosphoric acid.
  • the monocal solution may be produced by either combining phosphate rock, sulfuric acid and water or by dissolving superphosphate material (normal or triple) in water and separating any residue.
  • the phosphoric acid should have a concentration of between 10 and 30% P 2 0 5 and should be combined with an excess of phosphate rock to ensure that a near saturated solution of calcium phosphate is produced.
  • the phosphate rock itself is a well known and readily available source of phosphate values.
  • phosphoric acid is first mixed with a small amount of phosphate rock such as 10-20 parts phosphoric acid per part phosphate rock so as to neutralize any sulfuric acid, which is commonly employed in the manufacture of wet-process phosphoric acid.
  • a recycled stream of 10 to 40% gypsum based on the phosphoric acid/phosphate rock mixture may be added to enhance crystal growth during this step.
  • Gypsum may then be separated from the liquid using standard liquid/solid separation devices such as filters, centrifuges and the like.
  • Additional phosphate rock is then added in excess to the phosphoric acid in order to produce a soluble monocalcium phosphate solution. Generally, about 0.3 to 0.5 parts of additional phosphate rock are added per part of phosphate solution. The degree of calcium saturation will depend on the specific plant requirements. The excess rock present in the media during this reaction can be removed via clarification, filtration, etc. Final adjustment of the calcium/phosphorous ratio can be controlled by either the addition of rock or phosphoric acid to the monocalcium phosphate solution.
  • the prepared monocalcium solution is then sent to the ASD for contact with a potassium loaded ion exchange resin wherein a calcium loaded resin and potassium phosphates are formed.
  • a potassium loaded ion exchange resin wherein a calcium loaded resin and potassium phosphates are formed.
  • the flow rate of materials is highly dependent on the size of the ASD and can be ascertained quite readily.
  • a potassium chloride regeneration solution is fed into the ASD so as to form CaCl 2 brine and a regenerated potassium loaded resin.
  • the potassium chloride regeneration solution is preferably an aqueous solution containing at least 5% potassium chloride and preferably at least 18% potassium chloride. It will be appreciated that similar potassium salts may be used so long as the corresponding calcium or other metal salt is water-soluble. It has also been observed that hydrogen exchange occurs during this transfer. Following the regeneration step, the resin is again washed for subsequent loading with the calcium phosphate solution.
  • the process may be carried out at any temperature above freezing and below boiling although the preferred range is 27-71°C (80-160 O F1
  • the ASD itself which is fully described in the above- cited application is illustrated in Fig. 2. It comprises a plurality of fixed feed ports 12, to each of which may be supplied various feed materials. In the case of the present invention, these materials include the monocal solution, the washwater feeds and the potassium chloride regeneration fluid.
  • the ion exchange material is a commercial strong or weak cation resin such as the C-26 (strong cation) resin marketed by Rohm & Haas.
  • each feed port 12 has a corresponding discharge port 16. After the interaction product passes through a given fixed discharge port, it may be purged from the system, recirculated back to a selected feed port, or a combination of both.
  • the monocal solution, the washwater feeds, and the potassium chloride regeneration solution are each transported to given stationary feed ports so that the resin will be loaded with potassium, washed, contacted with monocal ion exchange solution whereby the potassium from the resin is exchanged with the calcium in the solution, re-washed, then re-loaded with potassium.
  • At least two fixed feed ports and corresponding fixed discharge ports should be provided for both the ion exchange and the regeneration stages.
  • the interaction products formed from the feed materials and the resin and discharged through a first ion exchange or regeneration discharge port can be fortified or treated in an intra-stage fashion with fresh feed or treatment materials for delivery into a second fixed ion exchange or regeneration feed port.
  • a second interaction product formed from the fortified solution entering fixed ion exchange feed port 12B and the potassium loaded resin may likewise be fortified with still more calcium phosphate material prior to delivery to a third fixed ion exchange feed port. This can be contained until the desired ratio of K 2 0/P 2 0 5 has been attained.
  • the same intra-stage addition of fresh feed materials may be practiced during the regeneration stage.
  • a solution of potassium chloride is fed into a first fixed regeneration feed port and passed through the calcium loaded resin to form an interaction product containing calcium chloride and reduced levels of potassium chloride, that product may likewise be fortified with additional fresh potassium chloride before delivery into a second fixed regeneration feed port.
  • a pH adjusting material may be added in an intra-stage fashion during the regeneration stage to effect neutralization of hydrogen ions generated during the exchange process so as the maximize the reaction efficiency.
  • one or more feed parts will have no fresh materials being supplied thereto but rather, will merely receive effluent which has not been fortified.
  • the number of chambers and fixed feed and discharge ports is a matter of design choice depending on the types of feed and regeneration materials, the type of resin used, and the size of the ASD. It has been found that twelve to twenty-four inches of a strong cation resin give good results. The flow rates of feed materials are likewise a matter of design choice.
  • the ASD By virtue of the ASD, it is possible to carry out the contacting of resin and exchange material in somewhat of a differential fashion. More specifically, beyond enabling fortification of the treating fluids in an intra-stage fashion continuously and economically, the ASD essentially enables the process to be carried out with a continuous supply of fresh resin. Accordingly, many of the contraints attendant with conventional exchange systems, i.e., the size of the actual exchange zone and the maximum flow rate which may be achieved are not as limiting with the ASD.
  • the amount of calcium phosphate material added to the interaction product streams should be between about 0.1 and 0.5 parts by weight per part interaction product.
  • the final potassium phosphate solution is converted to dry potassium phosphate or ammoniated product by transporting it to a crystallization/granulation circuit.
  • the solution can be used as a feedstock to a liquid fertilizer production operation.
  • a set of differential contacting tests were conducted to simulate the intra-stage addition of a calcium phosphate material to the effluent (containing the potassium phosphate product as well as reduced levels of calcium phosphate) discharged from the column containing potassium-loaded resin.
  • the first effluent was then combined with additional dicalcium phosphate and any excess solids removed by filtration.
  • the amount of dicalcium phosphate added was enough to raise the percent P 2 0 5 from 29.61% to 32.07% and the percent C aO from 1.94% and 3.69%.
  • This fortified solution was then fed into a second column containing C-26 resin loaded with potassium. A small sample of this second effluent was analyzed.
  • the second effluent was then mixed with enough additional dicalcium phosphate to raise the percent P 2 0 5 from 28.08% to 29.20% and to raise the percent CaO from 2.55% to 4.05%.
  • the second effluent was then fed to a third column containing the potassium-loaded resin.
  • the first 200 ml and the second 200 ml of the effluent from the third column were then separately analyzed.
  • the use of intra-stage (or incremental) addition of a calcium source does allow for a progressive increase in the K 2 0/P 2 0 5 ratio when compared to a single pass situation.
  • the process may be carried out advantageously in the ASD which makes it possible to simultaneously and continuously add feed materials in an intra-stage fashion to the various effluent streams i.e., during the loading, unloading and washing stages.
  • feed materials in an intra-stage fashion to the various effluent streams i.e., during the loading, unloading and washing stages.
  • the yield of product in the second 200 ml of effluent discharged from the third ion exchange column is significantly lower than that obtained in the first 200 ml increment of the third column.
  • This decrease demonstrates the low loading capacity of the C-26 resin.
  • such a low loading capacity resin although suited for potassium exchange, would nonetheless not be suited to conventional ion exchange systems such as fixed beds due to the unduly large volumes of resin which would be required as well as the difficulties associated with controlling the various flows when incremental fortification of feed materials between the exchange columns is desired.
  • the nature of the ASD effectively allows carrying out the potassium phosphate ion exchange process with low capacity ion exchange resins such as C-26.
  • Example 1 To further demonstrate the benefits derived from intra- stage additives of feed materials to effluent streams, the same tests were conducted as were done in Example 1 except that a 10% P 2 O 5 solution was prepared by leaching commercial superphosphate material with water.
  • Each chamber was 305 - 355mm filled with approximately 12-14 in.)of the C-26 strong cation resin (1.3 liters).
  • the unit was rotated at a rate of 20 minutes per revolution. The process was carried out at room temperature.
  • the ASD also had 12 fixed feed and discharge ports.
  • the potassium phosphate product was discharged through fixed discharge port 6.
  • the feed solution for the test was prepared by mixing a 10% solution of technical grade phosphoric acid with dicalcium phosphate and by then allowing the mixture to clarify.
  • the regeneration solution was made from industrial grade potassium chloride.
  • the level of K 2 0 in the phosphate solution could be increased by the injection of calcium ion between contacting stages, e.g. adding calcium to the no. 4 and/or no. 5 effluents.
  • the exact configuration, number of stages of contact, degree of intrastage potassium phosphate or regeneration solution treatment and the like will, of course, depend on specific plant or process requirements.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Treatment Of Water By Ion Exchange (AREA)
  • Manufacture Of Macromolecular Shaped Articles (AREA)
EP85308710A 1985-06-24 1985-11-29 Verfahren zur Herstellung von Kaliumphosphat durch Ionenaustauschen Ceased EP0205708A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US748187 1985-06-24
US06/748,187 US4704263A (en) 1985-06-24 1985-06-24 Production of potassium phosphates by ion exchange

Publications (2)

Publication Number Publication Date
EP0205708A2 true EP0205708A2 (de) 1986-12-30
EP0205708A3 EP0205708A3 (de) 1988-02-24

Family

ID=25008399

Family Applications (1)

Application Number Title Priority Date Filing Date
EP85308710A Ceased EP0205708A3 (de) 1985-06-24 1985-11-29 Verfahren zur Herstellung von Kaliumphosphat durch Ionenaustauschen

Country Status (10)

Country Link
US (1) US4704263A (de)
EP (1) EP0205708A3 (de)
JP (1) JPS61295214A (de)
KR (1) KR920010083B1 (de)
CN (1) CN85108744A (de)
AU (1) AU573512B2 (de)
CA (1) CA1262030A (de)
ES (1) ES8702299A1 (de)
IL (1) IL77059A (de)
IN (1) IN164570B (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0230355A3 (de) * 1986-01-14 1988-03-02 Advanced Separation Technologies Incorporated Verfahren zur Herstellung von Dialkalimetallphosphaten durch Ionenaustausch
EP0240143A3 (de) * 1986-04-04 1989-02-08 Advanced Separation Technologies Incorporated Verfahren zur Beseitigung von Fluoriden und Phosphortypsschmutz aus säurehaltigem Abfallwasser
WO1991005324A1 (en) * 1989-10-06 1991-04-18 Hl Display Ab A device for holding strip-like information carriers
WO2005066071A1 (fr) * 2003-12-24 2005-07-21 Ecophos Procede de preparation de phosphates de bases fortes

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5110578A (en) * 1989-10-05 1992-05-05 Monomeros Colombo Venezolanos, S.A. (E.M.A.) Continuous production of potassium nitrate via ion exchange
JP3152416B2 (ja) * 1996-12-12 2001-04-03 株式会社 伊藤園 茶の製造方法
FI107330B (fi) * 1999-12-03 2001-07-13 Kemira Agro Oy Kahden alkalimetallisuolan valmistaminen yhdistetyllä ioninvaihto- ja kiteytysmenetelmällä
US6822033B2 (en) 2001-11-19 2004-11-23 United States Gypsum Company Compositions and methods for treating set gypsum
US7374740B2 (en) * 2005-03-31 2008-05-20 Cargill, Incorporated Process for producing high purity phosphates
US8070895B2 (en) 2007-02-12 2011-12-06 United States Gypsum Company Water resistant cementitious article and method for preparing same
US8329308B2 (en) 2009-03-31 2012-12-11 United States Gypsum Company Cementitious article and method for preparing the same
CN106219581A (zh) * 2016-07-22 2016-12-14 中国科学院青海盐湖研究所 一种利用选择吸附法制备硝酸镁的方法
CN114057171B (zh) * 2021-11-30 2023-02-21 太仓沪试试剂有限公司 一种磷酸钾盐的纯化工艺

Family Cites Families (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3231492A (en) * 1962-05-16 1966-01-25 Universal Oil Prod Co Fluid-solid contacting process
US3956464A (en) * 1970-10-16 1976-05-11 Pennzoil Company Preparation of phosphates
US4012491A (en) * 1971-10-19 1977-03-15 United States Gypsum Company Phosphate process
JPS49106891A (de) * 1973-02-12 1974-10-09
US4024225A (en) * 1973-11-02 1977-05-17 United States Steel Corporation Method of making high purity alkali metal phosphates from wet-process phosphoric acid
DE2461064C2 (de) * 1974-12-23 1984-03-01 Hoechst Ag, 6230 Frankfurt Verfahren zur Herstellung reiner Alkaliphosphatlösungen aus Naßverfahrensphosphorsäure
US4008307A (en) * 1975-06-02 1977-02-15 Southwire Company Production of monobasic potassium phosphate by ion exchange
US4029743A (en) * 1975-12-24 1977-06-14 Hauge Douglas O Phosphoric acid manufacture
UST962001I4 (en) * 1976-10-06 1977-09-06 Tennessee Valley Authority Preparation of dicalcium phosphate from phosphate rock by the use of sulfur dioxide, water, and carbonyl compounds
US4293423A (en) * 1977-10-18 1981-10-06 Rohm And Haas Company Process and apparatus for ion exchange by use of thermally regenerable resin
US4412866A (en) * 1981-05-26 1983-11-01 The Amalgamated Sugar Company Method and apparatus for the sorption and separation of dissolved constituents
IT1168613B (it) * 1983-06-17 1987-05-20 Consiglio Nazionale Ricerche Impianto, ad elementi modulari, per lo smaltimento di rifiuti organici tramite vermicompostaggio
US4599225A (en) * 1983-12-15 1986-07-08 Internorth, Inc. Continuous flow separation with moving boundary sorption
US4591439A (en) * 1984-05-08 1986-05-27 E. I. Du Pont De Nemours And Company Ion exchange process and apparatus
US4522726A (en) * 1984-07-30 1985-06-11 Progress Equities Incorporated Advanced separation device and method

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0230355A3 (de) * 1986-01-14 1988-03-02 Advanced Separation Technologies Incorporated Verfahren zur Herstellung von Dialkalimetallphosphaten durch Ionenaustausch
EP0240143A3 (de) * 1986-04-04 1989-02-08 Advanced Separation Technologies Incorporated Verfahren zur Beseitigung von Fluoriden und Phosphortypsschmutz aus säurehaltigem Abfallwasser
WO1991005324A1 (en) * 1989-10-06 1991-04-18 Hl Display Ab A device for holding strip-like information carriers
WO2005066071A1 (fr) * 2003-12-24 2005-07-21 Ecophos Procede de preparation de phosphates de bases fortes

Also Published As

Publication number Publication date
ES549129A0 (es) 1987-01-01
CA1262030A (en) 1989-10-03
KR870000240A (ko) 1987-02-17
KR920010083B1 (ko) 1992-11-14
IN164570B (de) 1989-04-08
CN85108744A (zh) 1986-12-24
ES8702299A1 (es) 1987-01-01
JPS61295214A (ja) 1986-12-26
AU573512B2 (en) 1988-06-09
IL77059A0 (en) 1986-04-29
IL77059A (en) 1989-02-28
AU5054885A (en) 1987-01-08
JPH0446891B2 (de) 1992-07-31
US4704263A (en) 1987-11-03
EP0205708A3 (de) 1988-02-24

Similar Documents

Publication Publication Date Title
EP0205708A2 (de) Verfahren zur Herstellung von Kaliumphosphat durch Ionenaustauschen
JP2521748B2 (ja) 弗化物及び燐系汚染物質の除去方法
US4777027A (en) Continuous process for preparing phosphoric acid and calcium sulphate
US2799569A (en) Ammonium phosphate fertilizers
CN1064858A (zh) 用湿法磷酸联产肥料级和纯磷酸一铵
CA2016048C (en) Method for the production of potassium magnesium phosphate
US2897053A (en) Wet process for phosphoric acid manufacture
EP2928828B1 (de) Verfahren und vorrichtung zur herstellung von ammoniumsulfatkristallen
RU2634936C2 (ru) Способ получения комплексных минеральных удобрений из фосфатной руды и установка для его реализации
US4301130A (en) Method of washing waste phosphogypsum
GB2052467A (en) Preparation of multicomponent fertilizers
US3595610A (en) Manufacture of ammonium phosphates
EP1235743B1 (de) Herstellung zweier alkalimetallsalze durch ein kombiniertes ionenaustausch- und kristallisationsverfahren
US5021216A (en) Method of removing and crystallizing cation resin absorbed calcium and magnesium
US4002455A (en) Process for treating and recovering waste water from the fertilizer manufacture
US3993466A (en) Fertilizer production
EP0230355A2 (de) Verfahren zur Herstellung von Dialkalimetallphosphaten durch Ionenaustausch
FI105472B (fi) Monilietemenetelmä lannoitteen valmistamiseksi
RU2154045C1 (ru) Способ получения сложного минерального удобрения
US2849278A (en) Metal value recovery from phosphate rock
US3115390A (en) Method for preparing diammonium phosphate, starting from phosphoric acid produced by the wet process
US4678650A (en) Process for making an alkali phosphate solution
US3726660A (en) Nitrophosphate fertilizer production
US3118731A (en) Svanoe
RU2201414C2 (ru) Способ получения бесхлорных калийных минеральных удобрений

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): AT CH DE FR GB IT LI NL SE

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: ADVANCED SEPARATION TECHNOLOGIES INCORPORATED

PUAL Search report despatched

Free format text: ORIGINAL CODE: 0009013

AK Designated contracting states

Kind code of ref document: A3

Designated state(s): AT CH DE FR GB IT LI NL SE

17P Request for examination filed

Effective date: 19880805

17Q First examination report despatched

Effective date: 19891016

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN REFUSED

18R Application refused

Effective date: 19920627

RIN1 Information on inventor provided before grant (corrected)

Inventor name: ERICKSON, WILLIAM R.

Inventor name: BERRY, W. WES